Chloride Insertion–Immobilization Enables Bright, Narrowband, and Stable Blue-Emitting Perovskite Diodes

Abstract

Metal halide perovskites show promise for light-emitting diodes (LEDs) owing to their facile manufacture and excellent optoelectronic performance, including high color purity and spectral stability, especially in the green region. However, for blue perovskite LEDs, the emission spectrum line width is broadened to over 25 nm by the coexistence of multiple reduceddimensional perovskite domains, and the spectral stability is poor, with an undesirable shift (over 7 nm) toward longer wavelengths under operating conditions, degradation that occurs due to phase separation when mixed halides are employed. Here we demonstrate chloride insertion-immobilization, a strategy that enables blue perovskite LEDs, the first to exhibit narrowband (line width of 18 nm) and spectrally stable (no wavelength shift) performance. We prepare bromide-based perovskites and then employ organic chlorides for dynamic treatment, inserting and in situ immobilizing chlorides to blue-shift and stabilize the emission. We achieve sky-blue LEDs with a record luminance over 5100 cd/m 2 at 489 nm, and an operating half-life of 51 min at 1500 cd/m 2 . By device structure optimization, we further realize an improved EQE of 5.2% at 479 nm and an operating half-life of 90 min at 100 cd/m 2 .

High‐Performance Blue Perovskite Light‐Emitting Diodes Enabled by Efficient Energy Transfer between Coupled Quasi‐2D Perovskite Layers

“…Substantial efforts have been made in the past several years to obtain blue perovskite emitters, such as perovskite nanocrystals (NCs), [ 19–25 ] 2D perovskite nanoplatelets, [ 26–32 ] and quasi‐2D perovskites. [ 33–39 ] In particular, the quasi‐2D perovskites are rising as efficient luminescent materials for highly performed blue PeLEDs due to the cascade energy landscape for efficient exciton transfer and the subsequent radiative recombination. Typically, the quasi‐2D perovskites have a formula of B 2 (APbBr 3 ) n −1 PbBr 4 , where B is an organic spacer cation, A is a monovalent cation (e.g., Cs + , methylammonium (MA + ) or formamidinium, (FA + )), and n represents the number of lead halide octahedral layers.…”

Review of blue perovskite light emitting diodes with optimization strategies for perovskite film and device structure

“…7(a)). The maximum luminance and EQE of the sky-blue (487 nm) quasi-2D PeLEDs were 9048 cd/m 2 and 11%, respectively, which is one of the most efficient blue PeLEDs 98 . Ma et al adopted the chloride insertion−immobilization strategy by doping the organic halide diphenylphosphinic chloride (DPPOCl) into the precursor solution.…”

Interfacial Potassium‐Guided Grain Growth for Efficient Deep‐Blue Perovskite Light‐Emitting Diodes

“…Typically, halide engineering and dimensional engineering are the two main approaches to yield deep‐blue emission for PeLEDs. [ 24–27 ] Under continuous electrical excitation, rapid ion migration and 2D phase degradation will occur with the formation of halogen vacancies and the red‐shifted EL spectra of inorganic cesium lead halide (CsPbX 3 , where X = Cl, Br) perovskites. [ 10,20 ] To alleviate the spectral instability, several suitable materials have been explored as the precursor additives to stabilize the deep‐blue EL peaks for both colloidal perovskite quantum dots and quasi‐2D Ruddlesden–Popper perovskite thin films.…”